The use of microbial source tracking to assess and predict water quality in river catchments
Nnane, Daniel Ekane
PublisherUniversity of Brighton
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Abstract Water is a basic human need (Millennium Development Goal-Target 10) and a central element in all civilisations, yet microbial contamination of surface waters used for drinking, contact recreation, and shellfishery provides an effective vehicle for the spread of microbial waterborne diseases and outbreaks that can cause illness or death in humans. Microbial pathogens remain the most direct, real and pervasive risk to human health, especially in Less Economically Developed Countries. However, water quality managers are restricted in providing effective monitoring and management designs and strategies by the inability to identify routinely the source of microbial contamination. Microbial water quality of many surface waters is likely to deteriorate further as a result of climate change. This research used the River Ouse catchment (SE England) as a test-bed to investigate the application of simple and low-cost monitoring and approaches that can be applied in other river catchments, to monitor and manage microbial water quality during various meteorological conditions and seasons. This novel approach is the first time such methods have been combined in order to study a river catchment. As such, it represents a significant advancement in our understanding of complex environmental processes and ability to manage and mitigate adverse environmental impacts. Sixteen parameters were measured and analysed from 365 water samples collected approximately every fourteen days from fourteen discrete sampling sites. The chemophysical parameters were measured using recommended instruments and procedures whilst faecal indicator organisms (FlO) were enumerated using International Organisation for Standardisation (ISO) methods and procedures. In addition to ISO methods, the study trialled a newly developed low-cost phage-based method capable of identifying human faecal contamination in surface waters. The results showed that all sampling sites were microbially contaminated, and suggested that the main source. was non-human. Thermotolerant coliforms (TTC) and presumptive intestinal enteroCOCCI (ENT) levels tended to be 1.1-1.2 logs higher during rainstorm events. Spatio-temporal variations in microbial parameters were accounted for by three principal components (67.6%). Bacterial indicator decreased downstream while chemophysical parameters increased downstream. Models generated for TTC and ENT accounted for 63% and 65% variability in TTC and ENT levels respectively. Cluster Analysis of the fourteen sampling sites revealed six 'sentinel' sampling sites and this process is proposed as a means of rationalising river catchment monitoring. The correlation between TTC and phages of Bacteroides (GB-124) was very small (r=0.05) whilst those between turbidity, suspended solids, and bacterial indicators were significantly positively strong. Hence, turbidity could serve as a low-cost screening tool for microbial pollution. A capricious climate, animal and human interferences were likely faecal pollution sources. The findings offer low-cost screening approaches for river catchment management through the identification of 'when and where' pollution levels are most likely to represent a potential risk to public health under various meteorological conditions, and help those responsible for water quality monitoring to better target resources in future. These demonstrably effective approaches will contribute to future European collaborative work to improve waterborne FlO and pathogen prediction ('hotspots' of elevated waterborne disease risk during changing climate patterns), and future EU and WHO initiatives (such as Water Safety Plans) to improve environmental disease protection for all.